JP2012021224A - Method for preventing sludge generation in tin-plating solution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for efficiently preventing generation of sludge in a tin-plating solution when immersing a non-soluble anode and a copper or copper-alloy strip material in the tin-plating solution mainly consisting of inorganic acid, and executing the tin electroplating on a surface of the copper strip material at the high current density.SOLUTION: There are provided a tin-plating tank 1 in which a non-soluble anode and a copper or copper-alloy strip material are immersed in a tin-plating solution containing ethylene-diamine EO-PO addition product of 0.05-3g/l mainly consisting of inorganic acid and pyrogallol of 0.1-10g/l, and the tin electroplating is executed on a surface of the copper or copper-alloy strip material at the high current density, and a tin-plating solution circulating and storage tank 2. A part of tin-plating solution discharged from the tin-plating solution circulating storage tank 2 is supplied to a quadrivalent tin ion removing device 4 to reduce the quadrivalent tin ions into bivalent tin ions in the tin-plating solution, and the tin-plating solution with the quadrivalent tin ions being removed therefrom is supplied to the plating welding circulating storage tank 2.

Description

  The present invention immerses an insoluble anode and copper or a copper alloy strip in a tin plating solution containing an inorganic acid as a main component, and when performing tin electrolytic plating on the surface of copper or copper strip at a high current density, The present invention relates to a method for efficiently preventing sludge generated in the tin plating solution.

Conventionally, as a material for lead frames, terminals, and connectors used in semiconductor devices such as ICs and LSIs, various electronic and electrical components, copper or copper alloy strips with tin plating in which a tin plating layer is applied to copper or copper alloy strips are used. The material is widely used.
An inorganic acid bath such as a sulfuric acid bath or an organic acid bath is widely used as a tin plating bath used when a tin plating layer is applied to the surface of the copper or copper alloy strip. In these tin plating baths, an insoluble anode (anode) made of platinum, titanium, or the like and copper or a copper alloy strip as a cathode (cathode) are immersed and energized, whereby a copper or copper alloy strip ( Tin in the plating bath is electrodeposited on the surface of the cathode) and a tin plating layer is applied.
Here, when tin plating is performed under a high current density condition in an inorganic acid bath such as a sulfuric acid bath, a plating burn is likely to occur in the plating film, and in order to improve current efficiency under a high current density condition, a sulfuric acid bath, etc. When the temperature of the inorganic acid bath is increased, a large amount of sludge is generated mainly due to tetravalent tin ions formed by oxidation of divalent tin ions dissolved in the inorganic acid bath such as a sulfuric acid bath. In addition to the occurrence of plating stains (defective appearance), it also becomes a cause of hindering stable operation of the plating line. For this reason, how to efficiently remove sludge generated mainly by tetravalent tin ions is an important issue.

In Patent Document 1, a soluble metal and an inert electrode are respectively immersed in a solution containing tetravalent tin ions, and the soluble metal and the inert electrode are connected directly or with a conductor to connect the soluble metal to the negative electrode and the inert electrode. A battery having a positive electrode as a positive electrode is formed, the soluble metal is oxidized to metal ions and dissolved in a solution containing tetravalent tin ions, and the tetravalent tin ions in the solution are reduced to divalent tin ions. A tetravalent tin ion reduction method is disclosed.
In Patent Document 2, sludge accumulated at the bottom of the settling tank can be discharged out of the system in a short time without stopping the plating line, and the occurrence of defective plating contamination due to the sludge mixed in the plating solution. A plating solution supply facility that can be prevented is disclosed. This plating solution supply facility is a plating solution supply facility that supplies a tin plating solution from a circulation tank to a plating facility while circulating the metal between a metal dissolution tank, a sludge settling tank, and a circulation tank. A jet nozzle is provided in the settling tank, and the plating solution drawn from the settling tank by a jet pump is sprayed toward the bottom of the settling tank to break up the sludge. Sludge is taken out into a sludge tank and discharged out of the system.
In Patent Document 3, when electrotin plating is performed on steel or other metals with an acidic tin plating solution using an insoluble anode, the tin dissolution rate is increased, and the divalent ion concentration in the tin plating solution is within an appropriate range. And a method for reducing the generation of tin sludge is disclosed. The method uses a plating solution obtained by dissolving metallic tin in a tin dissolution vessel in which metallic tin is held and the plating solution temperature in the vessel is adjusted to 30 ° C. or more and less than 45 ° C. Electrotin plating method for performing electrotin plating, and dissolved oxygen concentration C (ppm)
Is an electrotin plating method in which metal tin is dissolved in a plating solution adjusted to be within a specific range, and electrotin plating is performed using the obtained plating solution.

JP-A-62-63692 JP 2008-266761 A JP 09-31699 A

When an insoluble anode and copper or a copper alloy strip are immersed in a tin plating solution containing an inorganic acid as a main component and tin electroplating is performed on the surface of the copper strip at a high current density, Patent Documents 1 to 3 are used. The method for preventing or removing sludge in the tin plating solution described in 1. is not sufficient in terms of efficiency and cost, and tin electrolysis at a higher density and higher flow rate is more recent. It was not fully compatible with the plating line.
In the present invention, when an insoluble anode and copper or a copper alloy strip are immersed in a tin plating solution containing an inorganic acid as a main component and tin electroplating is performed on the surface of the copper strip at a high current density, tin plating is performed. An object of the present invention is to provide a method for more efficiently preventing sludge generated in a liquid.

As a result of intensive studies, the present inventors have promoted a reduction reaction in advance in the tin plating solution in order to efficiently reduce tetravalent tin ions, which are the main cause of sludge in the tin plating solution, to divalent tin ions. It has been found that it is effective to contain an appropriate amount of an ethylenediamine EO-PO adduct as an agent.
In addition, in order to efficiently reduce tetravalent tin ions to divalent tin ions, it is necessary to remove dissolved oxygen in the plating solution, but it is dissolved using an expensive inert gas as in the past. Rather than removing oxygen, adding an appropriate amount of pyrogallol as a deoxidizer in advance in the tin plating solution to lower the dissolved oxygen concentration is cheap and efficient, and also occurs in the tin plating solution during tin plating. The present inventors have found that tetravalent tin ions can be more efficiently reduced to divalent tin ions by defoaming fine oxygen bubbles due to air intake.

  That is, the method for preventing the generation of sludge in the tin plating solution of the present invention includes ethylenediamine EO-PO adduct mainly composed of inorganic acid: 0.05 to 3 g / l and pyrogallol: 0.1 to 10 g / l. A tin plating bath for immersing an insoluble anode and copper or a copper alloy strip in a tin plating solution containing, and performing tin electrolytic plating on the surface of the copper or copper alloy strip at a high current density, and the tin plating A tin plating solution circulation storage tank for storing the tin plating solution extracted from the tank and circulating a part of the tin plating solution to the tin plating tank; A portion of the tin plating solution extracted from the tin plating solution is supplied to a tetravalent tin ion removing device to reduce the tetravalent tin ions in the tin plating solution to divalent tin ions. The tin plating solution from which ions have been removed is used as the plating solution. And supplying the ring reservoir.

The divalent tin ions in the tin plating solution of the tin plating tank are oxidized into air quaternary tin ions by air oxidation or electrolytic oxidation, and further converted into white colloidal hydroxide by hydrolysis reaction. It floats in the plating solution circulation storage tank or settles to form sludge. Before the tetravalent tin ions are hydrolyzed to form sludge, a part of the plating solution containing the tetravalent tin ions is supplied to a tetravalent tin ion removing device, and the tetravalent tin ions are divalent. If it is reduced to the tin ions and returned to the plating solution circulation storage tank, the concentration of quaternary tin ions in the tin plating solution is reduced, and the generation of sludge is effectively suppressed.
At this time, for example, tetravalent tin ions are reduced to divalent tin ions by a tetravalent tin ion removing device having a packed layer filled with metallic tin as a medium. For this purpose, it is effective to add 0.05 to 3 g / l of an ethylenediamine EO-PO adduct as a reduction reaction accelerator in advance in the tin plating solution, and further in the tin plating solution that hinders the reduction reaction. In order to remove dissolved oxygen, it is important to add 0.1 to 10 g / l pyrogallol as an oxygen scavenger in advance in the tin plating solution.
Further, the tetravalent tin ion removing device is a device in which the reaction medium and the tin plating solution are contacted in the reaction vessel, and the tetravalent tin ions are reduced to divalent tin ions. It is a packed bed form in which a tin plating solution is supplied from the bottom, and a tin plating solution from which tetravalent tin ions have been removed is extracted from the top, and spherical metal tin with a diameter of 1 to 30 mm is used as the reaction medium in the filling layer It is particularly preferable to do this. In this case, if the diameter of the spherical metallic tin is less than 1 mm or more than 30 mm, the effect as a reduction reaction medium is not sufficient. The medium filling rate and the empty cylinder speed in the packed bed may be appropriately changed according to the state of the tin plating solution, but the filling rate is 50 to 90% and the empty cylinder speed is 0.01 to 0.5 m / s. It is preferable.

Furthermore, the method for preventing the generation of sludge in the tin plating solution of the present invention, after defoaming a part of the tin plating solution extracted from the tin plating solution circulation storage tank by a defoaming device, It supplies to a tetravalent tin ion removal apparatus, It is characterized by the above-mentioned.
By defoaming fine oxygen bubbles due to the intake of air generated in the tin plating solution during tin plating, the tetravalent tin ions are removed from the tetravalent tin ions in a post-processing tetravalent tin ion removal device. Ions can be reduced more efficiently.

  Furthermore, the method for preventing the generation of sludge in the tin plating solution of the present invention is such that the tin plating solution contains sulfuric acid: 30 to 120 g / l, tin sulfate: 20 to 150 g / l, Oxyethylene styrenated phenyl ether: 0.3 to 6 g / l, polyoxyethylene naphthyl ether: 0.05 to 6 g / l, ethylenediamine EO-PO adduct as a reduction reaction accelerator: 0.05 to 3 g / l, desorption It contains pyrogallol as an oxygen agent: 0.1 to 10 g / l.

This tin plating solution has little foaming and less sludge generation when plating the surface of copper or copper alloy strips at a high current density. By applying to the method for preventing the generation of sludge in the tin plating solution of the present invention, the amount of foaming and sludge generation in the plating solution circulation storage tank is drastically reduced, the life of the plating solution is extended, and there is no plating burn. A good tin electrolytic plating film can be obtained.
The concentration of sulfuric acid is set to 30 to 120 g / l. If it is less than 30 g / l, the current density during plating does not increase, and if it exceeds 120 g / l, Sn becomes difficult to dissolve. More preferably, 60-90 g / l is good.
When the concentration of tin sulfate is 20 to 150 g / l, if less than 20 g / l, the current density during plating does not increase, and if it exceeds 150 g / l, the effect is saturated and the cost is wasted. More preferably, 60-120 g / l is good.
The concentration of polyoxyethylene styrenated phenyl ether is set to 0.3 to 6 g / l. If it is less than 0.3 g / l, the effect of suppressing plating burn and foaming is weakened, and if it exceeds 6 g / l, many bubbles are generated. Become. More preferably, it is 1 to 3 g / l.
The concentration of polyoxyethylene naphthyl ether is set to 0.05 to 6 g / l because if it is less than 0.05 g / l, the effect of suppressing plating burning, foaming and sludge is reduced, and if it exceeds 6 g / l, foaming is generated. Will increase. More preferably, 0.1 to 1.0 g / l is good.
The concentration of the ethylenediamine EO-PO adduct is 0.05 to 3 g / l. If it is less than 0.05 g / l, the effect is insufficient as a reduction reaction accelerator, and if it exceeds 3 g / l, bubbles are generated. Will increase. More preferably, 0.1 to 1.0 g / l is good.
The pyrogallol concentration of 0.1 to 10 g / l is not effective as an oxygen scavenger if it is less than 0.1 g / l. If it exceeds 10 g / l, foaming and sludge generation increase. More preferably, 2-5 g / l is good.

  According to the present invention, in a method of immersing an insoluble anode and copper or a copper alloy strip in a tin plating solution containing an inorganic acid as a main component and performing tin electrolytic plating on the surface of the copper strip at a high current density, tin plating is performed. A method for more efficiently preventing sludge generated in a liquid is provided.

It is a schematic block diagram which shows the example of the tin plating apparatus of one Embodiment of this invention. It is a cross-sectional view which shows the positional relationship of the electrode plate and copper strip in the tin plating tank of the tin plating apparatus of FIG.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
The tin plating apparatus includes a tin plating tank 1, a tin plating solution circulation storage tank 2, a defoaming device 3, a tetravalent tin ion removing device 4, and a tin ion supply device 5.
The tin plating tank 1 is provided with a power supply roll 13 for winding the copper alloy strip 11 so that the traveling direction of the copper strip 11 is bent between the horizontal direction and the vertical direction. Therefore, the copper alloy strip 11 is used as a cathode, and the electrode plate 12 in the tin plating tank 1 is used as an anode for energization. The power supply roll 13 is made of stainless steel, and SUS316, which is particularly excellent in corrosion resistance and wear resistance, is preferably used. The electrode plate 12 is an insoluble electrode plate in which titanium (Ti) is coated with iridium oxide (IrO ₂ ).

As shown by arrows in FIG. 1, the tin plating solution E is configured to flow through the tin plating tank 1 in the direction opposite to the traveling direction of the copper alloy strip 11 (indicated by solid arrows). The strip 11 and the tin plating solution E are moved relative to each other.
The tin plating solution E contains sulfuric acid: 30 to 120 g / l, tin sulfate: 20 to 150 g / l, and polyoxyethylene styrenated phenyl ether: 0.3 to 6 g / l as a brightener, polyoxyethylene naphthyl Ether: 0.05-6 g / l, ethylenediamine EO-PO adduct as a reduction reaction accelerator: 0.05-3 g / l, pyrogallol: 0.1-10 g / l as an oxygen scavenger, the balance being water It is the composition which consists of.
When this tin plating solution is subjected to tin electroplating on the surface of the copper alloy strip 11 at a high current density, it has less foaming, less sludge is generated, and plating burn hardly occurs. By applying this method to prevent the generation of sludge in the tin plating solution, the amount of foaming and sludge generated in the plating solution circulation storage tank is drastically reduced, the life of the plating solution is extended, and there is no plating burn. A simple tin electrolytic plating film is obtained.
The concentration of sulfuric acid is set to 30 to 120 g / l. If it is less than 30 g / l, the current density during plating does not increase, and if it exceeds 120 g / l, Sn becomes difficult to dissolve. More preferably, 60-90 g / l is good.
When the concentration of tin sulfate is 20 to 150 g / l, if less than 20 g / l, the current density during plating does not increase, and if it exceeds 150 g / l, the effect is saturated and the cost is wasted. More preferably, 60-120 g / l is good.
The concentration of polyoxyethylene styrenated phenyl ether is set to 0.3 to 6 g / l. If it is less than 0.3 g / l, the effect of suppressing plating burn and foaming is weakened, and if it exceeds 6 g / l, many bubbles are generated. Become. More preferably, it is 1 to 3 g / l.
The concentration of polyoxyethylene naphthyl ether is set to 0.05 to 6 g / l because if it is less than 0.05 g / l, the effect of suppressing plating burning, foaming, and sludge is reduced, and if it exceeds 6 g / l, foaming occurs. Will increase. More preferably, 0.1 to 1.0 g / l is good.
The concentration of the ethylenediamine EO-PO adduct is 0.05 to 3 g / l. If it is less than 0.05 g / l, the effect is insufficient as a reduction reaction accelerator, and if it exceeds 3 g / l, bubbles are generated. Will increase. More preferably, 0.1 to 1.0 g / l is good.
The pyrogallol concentration of 0.1 to 10 g / l is not effective as an oxygen scavenger if it is less than 0.1 g / l. If it exceeds 10 g / l, foaming and sludge generation increase. More preferably 2 to 6 g / l is good.

The tin plating solution E is extracted from the lower part of the tin plating tank 1 through the pipe 61 by the pump 50 and supplied to the tin plating solution circulation storage tank 2. In the tin plating solution circulation storage tank 2, the tin plating solution E is mixed with a tin plating solution G from which tetravalent tin ions have been removed as described later, and a part of the tin plating solution E is plated through the pipe 62 by the pump 51. It is supplied to the tank 1.
Most of the tin in the tin plating solution E supplied to the tin plating solution circulation storage tank 2 is tetravalent tin ions. If left as it is, the tetravalent tin ions are hydrolyzed to form white colloid. It becomes a hydrated hydroxide and floats or settles in a sludge state in the tin plating solution circulation storage tank 2. Therefore, before the tetravalent tin ions are hydrolyzed to form sludge, a part of the plating solution E containing the tetravalent tin ions is supplied to the tetravalent tin ion removing device 4 to provide the tetravalent tin ions. If ions are reduced to divalent tin ions and returned to the plating solution circulation storage tank 2, the concentration of quaternary tin ions in the tin plating solution is reduced, and sludge generation is effectively suppressed.

Therefore, in this tin plating apparatus, a part of the tin plating solution E in the tin plating solution circulation storage tank 2 is extracted from the lower part of the tin plating solution circulation storage tank 2 by the pump 52 and is firstly passed through the pipe 63. It is supplied to the defoaming device 3.
The defoaming device 3 is a device for defoaming fine oxygen bubbles in the tin plating solution E, and various defoaming devices can be applied, but also serves to remove dissolved oxygen in the tin plating solution E. In addition, for example, it is preferable to use a device such as a degassing pump / defoaming device ASP type manufactured by Yokota Manufacturing Co. The dissolved oxygen concentration in the tin plating solution E is reduced by adding 0.1 to 10 g / l pyrogallol as an oxygen scavenger in the tin plating solution E, and this type of defoaming apparatus is used. As a result, removal of 95% or more is possible.
Even without the defoaming device 3, the tin plating solution E has low foaming properties and few bubbles are generated. However, when used, the fine oxygen bubbles in the tin plating solution E are further reduced.

The tin plating solution F from which fine oxygen bubbles and dissolved oxygen have been removed by the defoaming device 3 is extracted by the pump 53 and supplied to the tetravalent tin ion removing device 4 through the pipe 64.
The tetravalent tin ion removing device 4 is a device in which the reaction medium and the tin plating solution F are brought into contact with each other in the container, and the tetravalent tin ions are reduced to divalent tin ions. The tin plating solution F is supplied and the tin plating solution G from which tetravalent tin ions are removed is extracted from the upper part, and a spherical metal tin having a diameter of 1 to 30 mm is used as a reaction medium in the packed layer. It is particularly preferred to use it.
In this case, if the diameter of the spherical metallic tin is less than 1 mm or more than 30 mm, the effect as a reduction reaction medium is not sufficient. The medium filling rate and the empty cylinder speed in the packed bed may be appropriately changed according to the state of the tin plating solution, but the filling rate is 50 to 90% and the empty cylinder speed is 0.01 to 0.5 m / s. It is particularly preferred.

The tin plating solution G from which tetravalent tin ions have been removed by the tetravalent tin ion removing device 4 is extracted by the pump 54 and returned to the upper portion of the tin plating solution circulation storage tank 2 through the pipe 65.
The tin plating solution G and the tin plating solution E are mixed in the tin plating solution circulation storage tank 2, the concentration of tetravalent tin ions in the tin plating solution circulation storage tank 2 is reduced, and the formation of sludge is suppressed, A part of the mixed solution is circulated by the pump 51 through the pipe 62 to the upper portion of the tin plating tank 1.
The tin plating solution circulation storage tank 2 is provided with a tin ion supply device 5 for supplying tin ions consumed in the tin plating tank 1. Divalent tin ions are appropriately supplied to the plating solution extracted through the pipe 65 and sent to the tin plating solution circulation storage tank 2.

Examples of the present invention will be described below.
In the tin plating tank, iridium oxide-coated titanium is used as the anode under the tin plating solution composition, temperature, and current density conditions shown in Table 1 so that the Reynolds number is 1 × 10 ^{4 to} 5 × 10 ^5. The copper alloy strip and the tin plating solution were moved relative to each other, and the copper alloy strip was subjected to tin plating.
In Table 1, A represents polyoxyethylene styrenated phenyl ether, B represents an ethylenediamine EO-PO adduct, C represents polyoxyethylene naphthyl ether, and D represents pyrogallol.
The Reynolds number Re is the relative velocity U (m / s) between the plating solution and the copper strip, the equivalent diameter De (m) of the flow field of the plating solution in the plating tank, and the kinematic viscosity coefficient ν (m2 / s) of the plating solution. From the relationship with s), Re = UDe / ν. The equivalent diameter De of the flow field of the plating solution is expressed by De = 2ab / (a + b) from the relationship between the width a of the electrode plate 29 and the distance b between the electrode plate 29 and the copper alloy strip 11 shown in FIG. Asked.
The tin plating solution storage amount in the tin plating solution circulation storage tank is set to 100 l, the circulation rate of the tin plating solution to the tin plating tank is set to 5 l / min, and the stored plating solution is extracted at a rate of 5 l / min, and vacuum vibration is performed. In addition, a tetravalent tin ion removing device (height 1000 mm x diameter 100 mm cylindrical packed bed, 20 mm diameter metal tin spheres using 20 kg, filling rate 70%, empty cylinder speed is 0.1 m / s), and the tin plating solution from which tetravalent tin ions were removed was returned to the tin plating solution circulation storage tank.
Examples 1-2 and Comparative Examples 1-2 are examples in which the vacuum vibration type defoaming device is not used, and Examples 3-8 and Comparative Examples 3-6 are examples in which the vacuum vibration type defoaming device is used. is there.

Under the conditions shown in Table 1, the generation and bubbling of the sludge in the tin plating solution circulation storage tank after observing tin plating for 120 hours was observed, and the plating burn on the surface of the obtained copper alloy strip with plating was observed. Observed.
For foaming, the foam height after 5 minutes at 25 ° C. was measured by the Ross Miles method according to JIS K 3362.
For sludge, the plating solution was collected from the Sn plating tank after the plating treatment, filtered and the amount of sludge was measured. The sludge amount was less than 5 g / l, and the sludge amount was less than 10 g / l. ◯ was 10 g / l or more and x.
Regarding plating burn, the surface of the plating material was visually observed, and the case where plating burn was not recognized was evaluated as “◯” and the case where plating burn was recognized as “×”.
These results are shown in Table 2.

  From the results shown in Table 2, the method for preventing the generation of sludge in the tin plating solution of the present invention can efficiently prevent the sludge generated in the tin plating solution. It can be seen that, by applying to, the amount of foaming and sludge generated in the plating solution circulation storage tank is drastically reduced, the life of the plating solution is extended, and a good tin electrolytic plating film without plating burn is obtained.

  As mentioned above, although the manufacturing method of embodiment of this invention was demonstrated, this invention is not limited to this description, A various change can be added in the range which does not deviate from the meaning of this invention.

DESCRIPTION OF SYMBOLS 1 Tin plating tank 2 Tin plating solution circulation storage tank 3 Defoaming apparatus 4 Tetravalent tin ion removal apparatus 5 Tin ion supply apparatus 11 Copper alloy strip 12 Electrode plate 13 Feed roll

Claims (3)

  An insoluble anode and a copper or copper alloy strip in a tin plating solution containing ethylenediamine EO-PO adduct containing 0.05 to 3 g / l and pyrogallol: 0.1 to 10 g / l containing an inorganic acid as a main component. A tin plating bath that is immersed and tin-plated on the surface of the copper or copper alloy strip at a high current density, the tin plating solution extracted from the tin plating bath is stored, and the tin plating is stored A tin plating solution circulation storage tank for circulating a part of the solution to the tin plating tank, and removing some of the tin plating solution extracted from the tin plating solution circulation storage tank with tetravalent tin ions The tetravalent tin ions in the tin plating solution are reduced to divalent tin ions by supplying to the apparatus, and the tin plating solution from which the tetravalent tin ions have been removed is supplied to the plating solution circulation storage tank. Of sludge in tin plating solution How to prevent the raw.   2. The tetravalent tin ion removing device is supplied to the tetravalent tin ion removing device after defoaming a part of the tin plating solution extracted from the tin plating solution circulation storage tank with a defoaming device. A method for preventing the generation of sludge in the tin plating solution.   The tin plating solution contains sulfuric acid: 30 to 120 g / l, tin sulfate: 20 to 150 g / l, and polyoxyethylene styrenated phenyl ether: 0.3 to 6 g / l as a brightener, polyoxyethylene naphthyl Ether: 0.05 to 6 g / l, ethylenediamine EO-PO adduct as a reduction reaction accelerator: 0.05 to 3 g / l, pyrogallol: 0.1 to 10 g / l as an oxygen scavenger The method of preventing generation | occurrence | production of the sludge in the tin plating solution of any one of Claim 1 to 2 to do.